Numerous challenges have been identified as critical for sustainability, including population growth, access to energy and resources, climate change, biodiversity decreases, and widespread poverty.Governments, industry, researchers, and advocates have proposed and begun to implement a range of actions and policies designed to tackle these challenges. Many of these practices are helpful for approaching sustainability, but their contributions typically do not match the scale of the challenges they aim to tackle. For example, recently the City of Pittsburgh announced plans to spend $24 million to replace 40,000 of its existing street lights with LED lights. This project is estimated to eliminate 17,853 tons of carbon dioxide (CO2) emissions per year (1), which of course is very helpful. However, this is only an approximately 0.7% reduction in the total CO2 emitted by the City (2). Although replacing street lights is likely to save the City money, such a small reduction in CO2 emissions contributes little to solving the challenge of climate change. That investment is probably better spent on educating people about how to save energy in their daily lives, such as by turning computers off when leaving their offices, which will have a larger impact at the City's scale. To meaningfully address climate change and other challenges, society needs a clear understanding of the magnitude of those challenges, and to match its actions to the scale of the problem.